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TM^T WORLD INTELLECTUAL PROPERTY ORGANIZATION

X X International Bureau

INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)

(51) International Patent Classification 6 :
G01N 27/02, 33/50

(21) International Application Number: PCT/IB 97/007 19

(22) International Filing Date: 15 April 1997 (15.04.97)

(11) International Publication Number: WO 97/39341

(43) International Publication Date: 23 October 1997 (23.10.97)

(30) Priority Data:
08/631,916

15 April 1996(15.04.96)

(71) Applicant: SOLID STATE FARMS, INC. [US/US]; 500
Winchester Drive, Reno, NV 89506 (US).

(72) Inventors: FULLER, Milton, E4 500 Winchester Drive, Reno,
NV 89506 (US). DEAMER, David, W.; 865 Pine Flat Road,
Santa Cruz, CA 95060 (US). IVERSON, Mark, N4 2225
Ridgeview Drive, Reno, NV 89509 (US). KOSHY, Ajit, J.
(deceased).

(74) Agents: CHICKERING, Robert, B. et ah; Flehr, Hohbach,
Test, Albritton & Herbert L.L.P., Suite 3400, 4 Embarcadero
Center, San Francisco, CA 941 1 1-4187 (US).

(81) Designated States: AU. CA, IP, KR, Eurasian patent (AM,
AZ, BY, KG, KZ, MD, RU, TJ, TM), European patent (AT,
BE, CH, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC,
NL, PT, SE).

Published

With international search report.

Before the expiration of the time limit for amending the
claims and to be republished in the event of the receipt of
amendments.

(54) Title: IMPROVING RADIO FREQUENCY SPECTRAL ANALYSIS FOR IN VITRO OR IN VIVO ENVIRONMENTS

(57) Abstract

Concentration of a target chemical, glucose, in the presence of other substances. Nad, in a specimen (4) is determined by subjecting
(2) the specimen (4) to radio frequencies (6, 16) up to about 5 GHz. The real and imaginary, components of the reflected and/or transrmtted
signal are examined (18) to identify the presence and/or concentration of the chemical of interest The examination includes anatysa
of the effective complex irnpedencc presented by the specimen (4) and/or the effective phase shift between the tiansmitted and reflected
signals. The effects upon glucose concentration measurements of Nad can be nulled-out by examining irnpedencc magnitude at a cross-
over frequency or measuring Nad cortcentration in a first frequency range and subtracting from a combined glucose/Nad concentration
measurement in a second frequency range. This technique can be advantageously used by diabetics to measure Wood glucose level.

FOR THE PURPOSES OP INFORMATION ONLY

Codes used to identify States party to the PCT on the front pages of pamphlets publishing international applications under the PCT.

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WO 97/39341

PCT7IB97/00719

IMPROVING RADIO FREQUENCY SPECTRAL ANALYSIS
FOR INATTRO OR IN-VTVO ENVIRONMENTS

RELATIONSHIP TO PREVIOUSLY FILED PATENT APPLICATION
This is a continuation-in-part of patent application serial no. 08/103,410, riled 6 August
5 1993 entitled APPARATUS AND METHOD FOR RADIO FREQUENCY SPECTROS-
COPY USING SPECTRAL ANALYSIS, now U.S. patent no. 5,508,203.

FIELD OF THE INVENTION
This invention relates generally to radio frequency spectroscopy, and more particularly to
improving specificity and accuracy of such analysis to determine the presence and/or
10 concentration of a desired chemical among other substances within a specimen.

BACKGROUND QF THE INVENTION
Many conventional analysis techniques measure the concentration of a chemical in a test
specimen or sample, even where the specimen contains a complex mixture of chemicals.
Such techniques include mass spectrophotometry, nuclear resonance, flame photometry,
15 conductance and refractometry. While these techniques work, unfortunately, their accuracy
is too often directly related to their cost. Further, many such techniques alter or destroy
the specimen under test, and require relatively elaborate equipment.

More recently attempts have been made to determine various properties of materials, using
sound, electromagnetic waves, or single pulses as the basis for analysis. In contrast to
20 conventional chemical analysis, wave and pulse-based techniques can provide a non-invasive
in-vivo analysis.

For example, U.S. Patent no. 4,679,426 (July 1987) discloses a non-invasive in- vivo tech-
nique for measuring concentration of chemicals, sodium chloride for example. Periodic
electromagnetic waves having a repetition rate of about 10 MHz to 100 MHz were coupled
25 to a subject's finger, and sodium or chloride ions within the finger apparently distorted
these waves. This distortion in the composite waveform was received from the finger,

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using the same electrode-antenna pair used to couple the waves to the finger. The
composite waveform distortion was then examined, and found to "provide meaningful data as
to chemical concentrations.

Glucose is an especially important chemical, a knowledge of whose absolute concentration
5 level can be vital to diabetics. Several techniques for providing blood-sugar analysts are
known, which permit subjects to detennine their own glucose levels. Unfortunately many
such techniques require invasive sampling of the subject.

One non-invasive technique for determining glucose levels in-vivo was disclosed in U.S.
Patent no. 4,765,179 (August 1988)in which a periodic train of electromagnetic energy,
10 preferably having a repetition rate of about 1 MHz to 1 GHz, was coupled to a subject's
finger. The composite waveform distortion was then analyzed and found to provide mean-
ingful analysis of glucose levels in the range of about 50 to 150 mg percent. However,
beyond about 110 mg percent, it was desirable to fine-rune the electromagnetic energy to
maintain measurement accuracy.

15 Understandably, blood is a complex solution. Monitoring the concentration of glucose in
blood presents substantial challenges to discriminate against other substances in the blood
that may mask or alter the analysis results.

U.S. patent no. 5,508,203 described a non-invasive in-vivo apparatus and method for deter-
rnining a chemical level in a subject, including the chemical glucose. The use of fre-
20 quencies up to about 1 GHz was disclosed and the disclosed apparatus permitted even lay
persons including diabetics to detennine, for example, the level of glucose in their blood
system.

As useful as the invention disclosed in U.S. patent no. 5,508,203 is, applicants have since
realized that electrolytes, e.g., Nad, KC1, Na 2 HP0 4 , and KHjPQt of varying concentra-

25 tions in human blood can affect the accuracy of glucose measurements using that invention.
In the human system, glucose concentrations typically range 60 mg/dl to about 150 mg/dl
for a non-diabetic, and range from about 50 mg/dl to 500 mg/dl. In the human population,
NaCl concentrations can range from about 135 mM to about 145 mM. To effectively and
confidently measure glucose and/or its concentration in blood, a resolution of about 10

3 0 mg/dl of glucose is desired. Non-invasive sophisticated laboratory grade test equipment can
resolve glucose hvvitro to perhaps 1.5 mg/dl. Invasive consumer-grade can resolve glucose

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to perhaps 5 mg/dl with an accuracy of perhaps ±10%. Applicants are not aware of
existing non-invasive devices for resolving glucose to the desired" 10 mg/dl level.

There is a need for a method and apparatus to reduce the varying concentration effects of
electrolytes, especially NaCl, when measuring glucose concentrations in human blood.
5 Such method and apparatus should be useable in-vitro and in-vivo, and should work in non-
invasive in-vivo measurement environments. Further, such method and apparatus should be
capable of use by lay persons. Such method and apparatus should also have applicability in
measurements unrelated to analysis of bodily fluid, including applications in industry.

The present invention discloses such a method and apparatus.

10 SUMMARY OF THE INVENTION

A specimen containing a chemical of interest as well as other substances is via probes
subjected to radio frequency electromagnetic signals having high frequency components ex-
tending to perhaps 5 GHz. Preferably such frequencies are sequentially presented using one
sinewave frequency at a time, although simultaneously presented multiple frequencies may

15 also be useful. Reflected and/or transmitted signal real and imaginary components at the
specimen are then spectrally examined as a function of frequency to identify the presence
and/or concentration of the chemical of interest. Such examination includes analysis of the
effective complex impedance presented by the specimen, and/or effective phase shift
between the transmitted and reflected signal at the specimen. In this manner, greater speci-

2 0 ficity can be attained with respect to detecting presence and/or concentration of a desired

analyte or chemical of interest.

For in-vitro measurements, a probe is inserted into the specimen and is coupled to a net-
work analyzer, or similar electronic system. In such in-vitro measurements, the specimen
may include blood or other bodily fluid, or may be a substance unrelated to bodily fluid.
25 In in-vivo measurements, a network analyzer of similar electronic system may be coupled
to electrodes) on a probe. The probe is pressed against a subject's body, preferably a
finger, and non-invasive analyses are made.

Applicants have discovered that variable concentrations of electrolytes, especially NaCl,
affect accuracy and specificity of glucose concentration measurements. At frequencies

3 0 below about 1 GHz, increasing NaCl (or other small ions) concentration decreases imped-

ance, whereas at higher frequencies the impedance is increased. Applicants believe that at
the lower frequencies, ions can respond to the changing electromagnetic field adjacent to
the probe ends, whereas this is more difficult at higher frequencies, whereat water dipoles

WO 97/39341 PCT/IB97/00719

appear to largely determine impedance. In general, applicants have learned that over a
wide frequency regime, higher glucose concentrations increases impedance, probably
because the large glucose molecules hamper movement of electrolyte ions and water dipoles
in a solution specimen. Of special interest, applicants have discovered that increasing NaCl
5 concentrations over a wide frequency regime increase phase shift in a linear fashion, which
phase shift is insensitive to glucose concentrations. Using these discoveries, applicants can
null-out or at least reduce or compensate for electrolyte concentration effects upon glucose
concentration by using cross-over frequencies, and by examining different measurement
parameters at different frequency regimes.

10 In a blood specimen, electrolyte concentration effects are effectively "tuned out* by

examining the magnitude of complex impedance using a cross-over frequency of approx-
imately 2.5 GHz. This use of a cross-over frequency and complex impedance measurement
provides low sensitivity to NaCl concentration and thus more accurate and specific glucose
concentration readings. Such analysis improvement can be highly important, for example

15 when the specimen comes from a diabetic or suspected diabetic.

Differential analyses may be made by combining impedance magnitude and phase shift
measurement data. For example, high frequency phase shift measurements taken between 2
GHz and perhaps 5 GHZ can provide data proportional to magnitude of ion concentration.

20 particularly NaCl. On the other hand, impedance magnitude measurements made using
lower frequencies, perhaps the 1 MHz to 400 MHz range, will provide a measure of
combined concentration of glucose and ion concentration, again primarily NaCl. The high
frequency phase shift data may be used to subtract out the effective NaCl concentration
from the lower frequency impedance total concentration data. The result is a lower

2 5 frequency measure of glucose concentration in the specimen, a frequency regime in which
measurement equipment is quite sensitive.

Analysis equipment coupled to the impedance measurement data and phase shift measure-
ment data can include look-up tables or the like, correlating phase shift data to NaCl
concentration levels. For industrial applications, the look-up tables can store data correlat-
30 ing impedance, phase shift and frequency measurements to known substances and con-
centration levels. This information can then be used to enhance nulting-out of NaCl in an
impedance measurement made at a cross-over frequency.

WO 97/39341 PCT/IB97/00719

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Output indicators coupled to such analysis equipment can enable even a lay user to readily
understand what chemical has been detected and at what concentration, or simply to
confirm that a safe concentration has been detected for the chemical of interest.

Other features and advantages of the invention will appear from the following description in
5 which the preferred embodiments have been set forth in detail, in conjunction with the
accompanying drawings.

BRIEF DESCR IPTION OF THE DRAWINGS
FIGURE 1 is a block diagram of a radio frequency spectroscopy system;

FIGURE 2 is a block diagram of the transmitter/receiver-signal processing system 14,
10 shown in Figure 1;

FIGURE 3A is a schematic of the calibration cell 66, depicted in Figure 2;

FIGURE 3B is a Smith chart impedance versus frequency representation of the equivalent
circuit depicted in Figure 3A;

FIGURES 4A, 4B, and 4C depict signal amplitudes provided by the system of Figure 1 for
15 different target chemicals in analyte test solutions;

FIGURE 5A depicts an in-vitro application of a radio frequency spectroscopy system with
enhanced analysis sensitivity, according to the present invention;

FIGURE 5B depicts an in-vivo application of a radio frequency spectroscopy system with
enhanced analysis sensitivity, according to the present invention;

20 FIGURE 6A compares non-invasive and invasive impedance magnitude test data for a
subject, using a test configuration according to Figure 5B;

FIGURE 6B shows correction for electrolyte dilution for the sam data shown in Figure 6A;

FIGURE 7A depicts linear relationship between electrolyte concentration and phase shift,
independently of glucose concentration;

25 FIGURE 7B depicts linear relationship between electrolyte concentration and phase shift in
a PBS solution, independently of glucose and/or albumin concentration;

WO 97/39341 PCT/IB97/00719

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FIGURE 7C demonstrates how improved specificity for a target analyte can be realized by
incl udin g measurements that are insensitive to a constituent in the specimen, for example,
phase shift measurements at 1.5 GHz to null-out albumin concentration;

FIGURE 7D depicts a phase cross-over frequency of about 20.1 MHz whereat phase shift
5 data is independent of glucose concentration;

FIGURE 8A depicts the increase in impedance measured from about 0. 1 MHz to about 1
GHz with increasing glucose concentration;

FIGURE 8B depicts a frequency regime in which increasing NaCl and glucose concentra-
10 tions increase impedance;

FIGURE 8C depicts a frequency regime in which increasing NaCl concentration does not
substantially affect impedance, but increasing glucose concentration increases impedance;

FIGURE 8D depicts a 2.0 GHz to 2.1 GHz frequency regime in which increasing NaCl
concentration decreases impedance, while increasing glucose concentration increases
15 impedance reasonably linearly;

FIGURE 8E depicts the non-linear behavior of impedance magnitude data over a 2.25 GHz
to 2.75 GHz frequency regime as NaCl concentration is varied, according to the present
invention;

FIGURE 8F depicts the existence of a cross-over frequency at about 2.5 GHz at which
20 NaCl concentration effects upon measured impedance are nuiled-out;

FIGURE 8G depicts frequency versus impedance changes for a specimen containing various
substances, and demonstrates a possible gamma globulin saturation region.

riPTATI F p DESCRIPTION OF THE PREF ^pFP EMBODIMENT
Figure 1 depicts a radio frequency ("RF") spectroscopy system 2 for detennining the

25 presence of one or more target chemicals (depicted as x, y) in a cell membrane specimen 4,
e.g., a human finger. The specimen finger 4 is pressed against a probe pair 6, preferably
disposed within a concave depression 8 formed in a lucite base 10. Probe pair 6 comprise
two conductive rods that protrude slightly from the depression 8, permitting electrical
contact to be made when finger 4 is pressed against the rods. Preferably the rods are

3 0 brass, perhaps 0.2' (5 mm) outer diameter and protrude outward from the concave surface

WO 97/39341 PCT/IB97/00719

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about 0.05" (1.3 nun), and into the lucite base about 0.5" (12 mm). Of course other tissue
could be probed, e.g., an ear, and the specimen need not be a human.

A pair of transmission lines 12 electrically couples the electrode pair to a system 14 that
includes a transmitter unit 16 and receiver-signal processor unit 18. Briefly, unit 16
5 transmits a high frequency signal via transmission lines 12 to probes 6, which couple the
signal to the specimen finger 4. Although the precise mechanism is not fully understood, it
appears that the presence of target chemicals, e.g., x and/or y. within the specimen may'
cause energy transfer of certain spectra of the source signal from transmitter 16. The result
is that a return signal from the specimen, present at probe pair 6 and coupled via transmis-
10 sion lines 12 to unit 18, differs from the source signal. Of course separate probe units 6
could be used to couple the transmitter unit 16 to the specimen, and to couple the return
signal from the specimen to unit 18.

Unit 18 receives and processes the return signal such that spectral signatures associated with
the presence and concentration of various target chemicals within the specimen can be

15 recognized. The processed data is then coupled to a display system 20 that conveys the
detected information to a user. Operation of the receiver-signal processor unit 18 can be
tailored, manually or automatically by a neural network, to recognize specific target chemi-
cals, for example glucose within the blood stream within finger specimen 4. In such
instance, the .various output devices within display system 20 might provide a user with

2 0 calibrated data as to his or her glucose concentration.

Display system 20 may include a monitor that can display a spectrum analyzer output
(22A). and/or alpha-numeric/graphical output (22B). Display system 20 may also include a
bar graph or alpha-numeric indicator 24 indicating, for example, the concentration level of
the target chemical, for example, glucose. A calibrated output meter 26 could provide the
25 user with concentration data. Alternatively, a simple "GO/NO GO" output indicator 23
could alert the user that excess glucose concentration has been detected. A diabetic user
would thus be alerted to take insulin immediately.

Figure 2 is a block diagram of the transmitter/recciver-signal processing system 14.
Oscillator 50 generates a high frequency stimulus signal that will be transmitted via probes
30 6 to specimen 4. In the preferred embodiment, oscillator 50 provides a 30 MHz funda-
mental square wave having a 50% duty cycle, and transition times of a few nanoseconds.
As such, the oscillator output frequency spectrum will be rich in harmonics, the odd-
numbered harmonics predominating. In the frequency domain, a perfect square-wave

WO 97/39341

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PCT/E997/00719

source signal would have harmonics with a sin(x)/x envelope, where x represents a
harmonic frequency.

The spectral output of such an oscillator 50 is commonly referred to as a comb spectra, as
the various spectra are uniformly spaced similar to the teeth on a comb. The power output
5 level at the oscillator output is preferably about 1 mW, which is 0 dBm, although other
power levels may also be used.

In the preferred embodiment, the various source signal spectra are harmonically related
since generation of a pulse train provides the harmonic frequencies automatically. However
the source frequencies need not be harmonically related, and a single oscillator 50 may be
10 rapidly changed between discrete frequencies (e.g., in the manner of spread spectrum

transmitters). Alternatively, oscillator 50 could comprise a plurality of signal generators
whose separate frequency outputs may or may not be harmonically related. If harmonically
related, one such generator could provide a sinusoidal output at a fundamental frequency,
e.g., 30 MHz. A second generator could provide a 60 MHz sinusoidal output, a third
15 generator could provide a 90 MHz sinusoidal output, and so forth. In a different

embodiment, one such generator might provide an output at frequency fl, a second genera-
tor might provide an output at f2, not harmonically related to fl, and so forth.

As used herein, oscillator 50 is understood to be a source of elearomagnetic signal that
contains a plurality of high frequency components, regardless of whether such components
2 0 represent harmonics of a single source frequency, or represent many source frequencies,
that need not be harmonically spaccd-apart.

Unit 52 preferably includes an amplifier stage and a power splitter, and comprises a MAR-
3 amplifier and a Cougar amplifier stage and a power splitter in the preferred embodiment.
These commercially available components boost the oscillator signal provided to divider 54
2 5 to about 15 dBm, and provided to power splitters 62, 64 to about 3 dBm. In turn, each
power splitter 62, 64 divides the thus amplified signal into two signals at nodes A and B,
each having 0 dBm power output. Splitters 62, 64 are preferably wideband, e.g., about 10
MHz to 1 ,000 MHz (or 1 GHz).

The intermediate frequency {'IF*) for system 14 is preferably 21.4 MHz, an intermediate
30 frequency commonly used in wmmercial equipment, for which frequency many stan-
dardized transformers and circuits are readily available. High-side mixing injection
preferably is used. Thus, to generate a local oscillator frequency that is 21.4 MHz higher

WO 97/39341 PCT/IB97/00719

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than a center frequency, it is necessary to develop a synthesized reference 6.4 MHz signal.
Unit 54 divides the fundamental frequency of the oscillator signal by 6, to yield a nominal
5.0 MHz reference signal.

This 5.0 MHz reference signal and a 6.4 MHz phase-locked crystal controlled oscillator
5 signal 58 are processed by offset module 56. Offset module 56 outputs on line 60 a signal
having a frequency of 6.4 MHz that is phase locked to the 30 MHz frequency of osrillator
50. Because phase lock loop systems are well known in the art of digital signal processing
design, further details of the generation of the frequency locked 6.4 MHz signal on line 60
are not presented here.

In Figure 2, calibrator unit 66 is an electronic model of a typical human finger, essentially
the electronic equivalent circuit of a finger specimen 4. While calibration unit 66
approximates the specimen impedance, unit 66 will not include the target chemical.

Figure 3A details the circuitry within calibration unit 66. namely two segments of
transmission line having 50 0 impedance at 400 MHz, and assorted resistors and capacitors.

15 The transmission lines, resistors and capacitors were selected empirically by comparing
frequency versus impedance data from human fingers with data from the equivalent circuit
of Figure 3A. Figure 3B is a Smith chart impedance versus frequency representation of the
equivalent circuit of Figure 3A. Point A in Figure 3B represents an impedance of about
192 0/-201 Q at 10 MHz, point B is 39.5 0/11.5 0 at 300 MHz, C is 52 Q at 400 MHz,

20 and point D is about 57 Q/-2.6 0 at 500 MHz.

With further reference to Figure 2, as will now be described, various components are
replicated to provide a processing path for the transmitted source signal, and to provide a
processing path for what will be termed the sampled return (or received) signal. The
2 5 sampled return signal advantageously permits compensating the system of Figure 2 for

component variations and drift between what will be. termed the received and the transmit-
ted signal processing paths.

More specifically, the response of specimen 4 to the source signal (e.g., the return signal at
the probe pair 6) is switchaWy sampled by switch SI with the response of the calibration
30 unit 66 to the source signal. Harmonic frequency-by-frequency, the output from probe pair
6 and from calibration unit 66 are sampled, the output of SI providing a sampled return
signal at node C to the remainder of system 18. Of course, if source oscillator 50 provided
discrete frequencies that were not harmonically related, it is understood that frequency-by-

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frequency, the output from probe pair 6 and from calibration unit 66 would be sampled. In
the preferred embodiment, the frequency bands of interest begin with about the sixth or
seventh harmonic of source oscillator 50, e.g., about 195 MHz, and extend to about 1
GHz, or higher, which range is the bandwidth of system 18. Within that bandwidth,
5 individual frequencies axe sampied between probe pair 6 and calibration unit 66.

Switch SI preferably is a commercially available monolithic microwave integrated circuit
("MMIC"), a relay, or other switching mechanism. SI switches between the probe 6
output and the calibrator under control of a microprocessor 74 within system 14. In the
preferred embodiment, microprocessor 74 was a Motorola 68HC11, although other
10 microprocessors could be used instead.

SI may sample the output of probe 6 for a time period ranging from perhaps 30 ms to
perhaps 7 seconds, and then may sample the output of the calibration unit 66 for a time
period also within that range, the duty cycle typically being aperiodic. For example, during
the time SI is coupled to probe 6, the probe output signal is sampled for one or more
15 frequencies that are harmonics of the fundamental frequency of oscillator 50 (or for one or
more discrete frequencies provided by an oscillator 50 that does not provide harmonics).
During the time SI is coupled to the calibration unit 66, the response of calibration unit 66
to one or more frequencies that are harmonics of the fundamental oscillator 50 frequency
are sampled.

2 0 Understandably, if components 76T and 76R, 78T and 78R, 80T, 80R, 90T and 90R (to be
described) were identical and exhibited no drift, calibration unit 66 could be dispensed with,
and SI replaced by a wire making a permanent connection in the probe 6 SI position. Such
an ideal system would require no mechanism for compensating for drift and other differenc-
es in the signal processing paths for the harmonics of the oscillator signal 50, and for the

25 harmonics in the return signal obtained from probe 6.

In practice, variations in temperature and/or pressure between probe pair 6 and the tissue in
the specimen 4 may contribute some error to the measurement process. To permit
microprocessor 74 to compensate for such error, in addition to providing the micropro-
cessor with phase and amplitude information for harmonics, phase and amplitude informa-
3 0 tion is also provided for the oscillator fundamental frequency. This frequency has been
found experimentally to be sensitive to such temperature and/or pressure variations. It is
understood that suitable teniperarure and/or pressure transducers and analog-to-digital
conversion components that are not shown in Figure 1 are used.

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As shown in Figure 2, withinjhe transmitted source signal processing path, a bandpass
filter 68T has a center frequency equal to that of oscillator 50, e.g., 30 MHz, and a
bandwidth of about 1 KHz to perhaps 1 MHz. Other bandwidths could be used and in fact,
a 30 MHz lowpass filter might instead be used. The transmitted signal from node A is
5 coupled to bandpass filter 68T, and the 30 MHz center frequency component of this signal
passes from filter 68T and is amplitude limited by limiter 70T. The thus bandpass filtered
and amplitude limited signal is coupled to an input of a phase detector 72.

In a parallel path, the sampled return signal from switch SI, present at node C, passes
through a similar 30 MHz bandpass filter 68R, amplitude limiter 70R to provide a second
1 0 input to phase detector 72. (The letter T or R attached to a reference element herein

denotes that the element is used in the transmitted source. path, e.g.. 68T, or is used in the
sampled return signal path, e.g., 68R.)

Phase detector 72 compares the difference in phase between the transmitted 30 MHz
fundamental frequency and the sampled return 30 MHz fundamental frequency signal. The
15 phase detector 72 output signal voltage will be proportional to such phase shift, e.g., a
number of mV per each degree of phase shift. As shown in Figure 2. the phase output
information from detector 72 is coupled to microprocessor 74 for analysis.

Proceeding horizontally across the top of Figure 2, parallel paths are also depicted for
processing the transmitted source signal harmonics (available at node B) and the sampled
20 return signal harmonics from switch SI (available at node C). These two horizontal paths
use substantially identical components (as denoted by the nomenclature) to provide
transmitted and sampled return signals at an intermediate frequency (IF) that is about 21.4
MHz in the preferred embodiment.

Briefly, the components now to be described resolve the harmonic frequency components of
25 the signals at node B and node C into preferably four bands of discrete frequencies, de-
pending upon what harmonics of the source oscillator signals are desired to be examined.

Much of the retnainder of the signal processor functions as a scanner-receiver, that under
microprocessor control scans discrete harmonic frequencies of interest. The transmitted
source signal path components will first be described, it being understood that identical
3 0 components are used in the parallel sampled return signal path, as indicated by the

nomenclature, e.g., 76T, 76R, 78T. 78R, etc. Bandpass filter 76T (and thus also 76R)
preferably is a filter bank that includes an internal MMIC switching mechanism operating

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under control of microprocessor 74. The input port of filter 76T passes the transmitted sig-
nal from node B through an internal switch into two banks of pre-shaping three-pole
bandpass filters. These first two internal filter banks have bandpasses of 195 MHz to 395
MHz t and 395 MHz to 805 MHz. Still within filter bank 76T, the outputs from the 195-
5 395 MHz and 395-805 MHz filters pass through additional internal MMIC switches and
bandpass filters. These additional filters pass 195-295 MHz, 295^05 MHz, 405-610 MHz,
and 605-815 MHz. Still within 76T, the variously filtered components are combined into a
single signal that is amplified by amplifier 78T.

In similar fashion, the sampled return signal at node C is passed through switching
10 bandpass filters within bandpass filter bank 76R, and the variously filtered components are
combined and amplified by amplifier 78R. While the operation of bandpass filter banks
76T, 76R has been described with reference to specific frequency bands, those skilled in
the art will recognize that the frequencies comprising the signals at nodes B and C may be
filtered using bandpass filters having different ranges of bandpass. Because the design of
15 units 76T, 76R is known to those skilled in the relevant art, schematics are not here
provided.

For example, if the target chemical of interest is best resolved by examining say the seventh
harmonic of the 30 MHz trarismiued source signal (or a given discrete frequency of a
source signal providing aplurality of frequencies not necessarily harmonically related),
20 microprocessor 74 is caused to control the switching within units 76T, 76R to pass 210
MHz frequency components, e.g., to select the 195 MHz-295 MHz bandpass. Amplifiers
78T, 78R preferably have sufficient gain to compensate for attenuation caused by filters
76T, 76R, and have a bandwidth of at least 195 MHz to 815 MHz.

Of course, if amplifiers 78T t 78R were ideal and not subject to front-end overload, it would
25 be possible to delete the bandpass filter systems 76T, 76R, and rely upon the operation of
mixers 80T, 80R, and narrow band IF units 90T, 90R (to be described), to separate the
various harmonic components of the oscillator signal and of the return signal.

As shown by Figure 2, the output signals from amplifiers 78T, 78R are provided as an
input signal to mixers 80T, 80R. Frequency synthesized local oscillators LOl or L02
3 0 provide respective second input signals to mixers 80T, 80R, via a MMIC switch S2 (or

similar device) that switches between the two synthesized oscillator signals under control of
microprocessor 74.

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The synthesized LOl or L02 signals are then frequency mixed agains, the selective spectral
components of the transmitted source signal and sampled return signal that have been
switchably selected to pass through filter banks 76T, 76R. The LOl or L02 output signals
are 21.4 MHz above the harmonic frequency of interest. Because of the difficulty associ-
5 ated with implementing a synthesized local oscillator whose output frequency can range
from about 231.4 MHZ (e.g., 7x30 MHz + 21.4 MHz) to perhaps 800 Mhz (e g about
the twenty-sixth harmonic 26x30 MHz + 21.4 MHz), the preferred embodiment employed
two local oscillators, LOl, L02. If, however a suitable synthesized oscillator having a
twooctave frequency output could be implemented, such oscillator would replace LOl,
10 L02 and the necessity for S2.

Stages 90T, 90R are narrowband intermediate frequency circuits that pass a 21.4 MHz
center frequency with a bandwidth of about 25 KHz. Of course by suitably offsetting
mixing frequencies, an IF of other than 21.4 MHz could be used. In the preferred
embodiment, IF units 90T, 90R are similar to IF units commonly found in commercially
15 available cellular telephones.

The harmonic frequency information passing through IF units 90T and 90R are input to
phase detector 92. Phase detector 92 compares transmitted source and sampled return
signals at each harmonic frequency of interest. The difference in phase between these
signals is then provided by phase detector 92 to microprocessor 74. At the same time, the

2 0 relative voltage levels from the IF units 90T, 90R at node D are also provided (after suit-

able analog to digital conversion, converter not shown) to microprocessor 74.

To recapitulate, microprocessor 74 receives phase information from detector 92 that is
relative to the various harmonics of the source signal (or discrete frequencies of interest if a
non-hannonic generator 50 is employed), and that is relative to the various harmonics (or
discrete frequencies) of the source signal as altered by the target substance and received at
the probe pair 6. Similarly, microprocessor 74 receives amplitude information of IF units
90T and 90R relative to the various harmonics (or discrete frequencies of interest) of the
source signal, and that is relative to the various harmonics (or discrete frequencies) of the
source signal as altered by the target substance and received at probe pair 6. Further, to

3 0 permit compensation for probe temperature and/or probe-specimen pressure variations'.

limiters 70T, 70R provide microprocessor 74 with amplitude of the source frequency, and
with amplitude of the source frequency as altered by the target substance and received at
probe pair 6, while detector 72 provides similar phase information for the source fre-
quency.

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Microprocessor 74 operates under program control, generating data for further processing
by a so-called neural network, look-up table, algorithm, or other method of signal process-
ing, shown symbolically in Figure 2 as element 100. In a manner known to those skilled in
the relevant art, a neural network 100 can be "trained" to recognize a spectral signature
5 associated with a given target chemical, glucose for example. To ease this recognition,
neural network 100 can optimize the manner of signal processing within unit 14.

For example, the operation of filter banks 76T, 76R can be altered under control of
microprocessor 74. In a more generalized embodiment, the number and bandwidth of indi-
vidual bandpass filters within units 76T, 76R could be dynamically modified by suitable

10 MMIC-selection, all under microprocessor control. However, unit 100 may simply be a
look-up table, correlating relative amplitude changes in a return signal with harmonic
frequency against presence or concentration of a target chemical in the specimen. Further,
a suitable neural network 100 might control microprocessor 74 to optimize the generation of
discrete frequencies, based upon processed signature data. For example, if a certain set of

15 frequencies from oscillator 50 provided a slight spectral signature, network 100 might direct
oscillator 50 to provide slightly different frequencies until the signature was more recogniz-
able.

Microprocessor 74 in turn provides output signals to output indicators) 20. As has been
described, output indicators) 20 can, in a variety of formats, display information enabling a

20 user to determine the presence and concentration of a desired target chemical (e.g., x) in a
specimen. In the preferred embodiment, the specimen is in fact a finger of the individual
using the disclosed system. Although the system shown in Figures 1 and 2 was
implemented in breadboard fashion, those skilled in the art will appreciate that it may in
fact be fabricated in a handheld, battery operated, portable unit. In such embodiment,

25 output indicators) 20 would preferably include liquid crystal displays (LCDs) or simple

GO/NO GO indicators, to preserve power and space. Preferably base 10 would be attached
to the case housing the remainder of the system for ease of portability.

Figures 4A and 4B represent multiple averaged in-vitro data obtained with the system of
Figures 1 and 2, using as a test specimen whole blood (e.g., red blood cells) to which glu-
30 cose or lactose or sucrose or urea or NaCl was added as a test chemical. The test cells
were compared to a calibrated cell that contained only red blood cells. Figure 4C repre-
sents similar data for whole sheep's blood (e.g., no glucose), and for sheep's blood with
various concentrations of glucose, where the nomenclature 'Blood 102" denotes 102 mg-%
or 102 mg per dL glucose. Typically, a healthy human has perhaps 80-120 mg% glucose,

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whilc a diabetic has 2CXM00 mg-% glucose. The vertical axis in Figure 4C represents the
vector amplitude the return signal, taking into account magnitude and phase. The
horizontal axis represents harmonics of a 30 MHz source frequency, the first harmonic
being at 210 MHz.

To minimize probe-related variables, the specimens in Figures 4A, 4B and 4C were tested
using parallel plate capacitive cells. These cells comprised two dielectric substrates having
a relative permittivity approximating that of water (= 80). with art electrode surface baked
onto each substrate. The test substance was placed in a chamber between the substrates.

The varying degree of signal amplitude shown in Figures 4A. 4B, and 4B are termed
10 "spectral signatures". What is depicted is the difference in amplitude between the cali-
brated cell (analogous to the use of the calibration^! 66 in Figure 2) and the test
specimen (analogous to the use of probes 6 and specimen 4 in Figure 1). These data
indicate that the system of Figures 1 and 2 may be used to discern the presence of a target
chemical within a test specimen or sample.

A preferred application is the detection of excess glucose in a user's blood, e.g.. within the
specimen. Because the present invention operates non-invasively, it suffices for the user to
press his or her finger against the probe pair 6, as shown in Figure 1. In response to the
. high frequency, high harmonic content signal from transmitter 16, chemicals within the
specimen can recognizably cause energy transfer of certain spectral components of the
transmitted source signal. It is hypothesized that within the specimen, the target chemical
glucose interacts with the lipid bilayer and/or red blood cell membranes.

Thus, in the presence of frequency components from the signal transmitted via probes 6,
the glucose seems to bring about non-linear mternmdulation or mixing of frequency compo-
nents, possibly due to a non-linear dielectric phenomenon involving capacitance associated
25 with glucose. Using the system of Figures 1 and 2, a diabetic user may rapidly obtain

glucose concentration level information. Signal processing by unit 18 would, essentially in
real time, provide glucose level information on display unit 20.

Of course other target chemicals may also be detected, including for example fructose,
galactose, alcohol. For example, a system according to what is disclosed herein may be
30 used to sense alcohol in a motorist's system, either by a motorist before attempting to
drive, or by a police officer attempting to determine whether an individual is under the
influence of alcohol.

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Because the disclosed system of Figures i and 2 appears to be sensitive to boundary
conditions at a lipid bilayer membrane, disruptions to such boundary conditions may be
detected by a spectral signature. Thus, the presence of glucose in varying amounts at a
membrane may be detected.
5 In a different utility, however, trauma to a specimen that interferes with such boundary
conditions may also be detected, primarily for the purpose of providing medical treatment.
For example victims of electrocution may received localized injuries, for example on an
arm. Unless the injury sites are promptly treated by the injection of certain medication that
is potentially rather toxic, the victim will lose the injured limb or die. Use of the invention
10 disclosed herein would permit diagnosis of such injury sites, and quantizing the injury to
facilitate prompt and accurate medical treatment.

Subsequent to the invention described with reference to FiguresMB, applicants came to
appreciate the role that changing electrolyte concentrations can have upon glucose
concentration measurements in blood specimens. Applicants further discovered that it is
15 possible to improve analysis for a desired chemical by reducing the effects upon such analy-
sis of varying concentrations of other substances in the specimen.

Figures 5A and 5B respectively show in-vitro and in-vivo applications of improved analysis
using a system 200, according to the present invention. In Figure 5A, preferably two
probes 202A, 202B are coupled by short lengths of coaxial cable 12 to ports A and B of a
20 frequency generator and analyzer system 250. In general, the transmitted signal is sent
from port A or port B, and a portion of the transmitted signal is reflected by the specimen
back into the transmitting port. In transmission mode (e.g., Figure 5B), port B returns the
fraction of the signal transmitted via port A through the subject's finger.

In the embodiments of Figures 5A and 5B, cables 12 preferably are 20 cm or less lengths
25 of coaxial cable, and probes 202A, 202B preferably arc Hewlett Packard HP 85075B di-
electric probes. These probes are coaxial in construction, having an outer diameter of
perhaps 2 cm and a probe length of perhaps 3.8 oil The probes have a center conductor
that is surrounded by a groundplane sheath at the probe tip. However, other cable
couplings and probes could also be used.

30 As will be described, system 250 includes a transmitter unit 260 that can output discrete
sinusoidal waveforms that are spaced-apart in frequencies linearly or logarithmically in
user-selectable steps. Further, the output frequencies are stepped between user-selectable
lowermost and uppermost frequencies f t and 4. respectively. In the preferred embodiments,

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f, was about 300 KHz, C was about 3 GHz, with approximately 801 linearly-spaced
frequencies output between f, and Applicants believe, however, that an / of about 5
GHz would also be useful to the present invention. In the preferred embodiment, system
250 was implemented using a commercially available Hewlett Packard HP 8753A network
5 analyzer with an HP 85046A S-parameter test set. However, other systems implementing
similar functions could be used instead.

System 270 farther contains a receiver and signal processor unit 270 that analyzes
waveforms associated with signals transmitted by and/or at least partially reflected back to
system 270. The waveforms under analysis are associated with discrete user-programinable
1 0 frequencies. The analysis can examine real and imaginary components of these waveforms,
including complex (e.g., having real and imaginary components) reflection coefficient data.
These various data are signal processed by unit 270 to provide information including
complex impedance magnitude (Z), phase shift, and/or permittivity.

Among the electrolytes, NaCl has the most significant influence on measurements, in that
15 its normal concentration range in the human body is 135-145 mM (millimolar), whereas
KC1, by example, is only abut 4-10 mM. Substances such as urea were confirmed to not
influence glucose measurements, probably because urea has a molecular size that is one-
third that of glucose, and has a physiologically controlled concentration ranging from 5-40
mg/dl. The range of glucose in a human normally is about 50 mg/dl (or mg%) to 150

2 0 mg/dl, and can reach about 500 mg/dl in a diabetic.

In Figure 5 A, probe 202 contacts a specimen of interest 204, perhaps about 40 ml, retained
within a beaker or receptacle 206 whose volume is perhaps 100 ml. Specimen 204 includes
a chemical of interest denoted X, as well as one or more other substances, denoted
collectively Y. In a preferred embodiment, specimen 204 is a bodily fluid, for example
25 blood, X is glucose (whose presence and/or concentration is to be detennined), and Y may
include varying concentrations of blood electrolytes such as NaCl, Na 2 HP0 4 , KC1, and
KH 2 P0 4 , as well as proteins and lipids.

Although large concentrations of proteins and lipids are also found in blood, the human
body maintains relatively tight control over variations in such substances, and thus their

3 0 presence appears not to substantially affect measurements according to the present in-

vention.

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In an industrial application, specimen 204 may be a solution in which X and Y represent
different chemicals, in which the presence and/or concentration of X is to be discerned, for
example to confirm quality control of the production of solution 204.

A second container 210 into which probe 202B is inserted contains a test or control solution
5 208 that intentionally lacks at least one chemical found in specimen 204. Both specimens
preferably are retained at a same temperature by partially immersing containers 206, 210 in
a preferably constant temperature bath 212 maintained within a larger beaker or container
214.

In Figure 5A, analyzer unit 250 is operated with signals at ports A and B in a reflectance
10 mode, e.g., in which signals transmitted out of each port are at least partially reflected back
into the ports by the respective specimens. From the real and imaginary components of the
reflected signal data, useful information as to the presence and concentration of at least one
chemical in solution 204 may be determined, according to the present invention.

Applicants have discovered that the real and imaginary components of the reflected signals
15 can be affected by the nature and content of the specimen solutions in the immediate

vicinity of the tips of the probes. What is believed to occur is mat fringing fields extend
from the center conductor of the preferably dielectric probes to the surrounding ground
plane. As the properties of the specimen solutions change, e.g., due to the presence and
concentration of one or more chemicals or other substances therein, the fringing field is
2 0 affected. The alterations to the fringing field in turn affect the reflected signals being
returned to ports A and/or B of the analyzer unit 250.

The complex data gathered and processed by unit 250 is coupled as input to a computer unit
280 for further processing. If desired, computer unit 280 may include any or all of the
output indicators 22A, 22B, 24, 26, 28 described earlier with respect to Figure 1, as well
25 as any other output indicators) that may be desired.

Computer unit 280 may be a personal computer executing a software routine permitting
conversion of the real and imaginary data it receives into forms including the magnitude of
the effective complex impedance Z presented by the specimen, phase shift between signals
transmitted and at least partially reflected back by the specimen, effective permittivity, and
30 the like.

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In the preferred embodiment, computer 280 executed Excel spreadsheet software to convert
the incoming complex data into more useful form. A modified Bao procedure was adopted,
in which complex impedance (Z) is determined from the complex reflection coefficient (T)
at the interface between the flat end of a probe, e.g., 202A, and a specimen solution, e.g.,
5 204.

1 + r

—.TT7 (1)

The characteristic impedance Z, of coaxial line 12 may be calculated from the relationship:

Z =377

(2)

in which 377 represents impedance of air, b is the outside diameter of the probe, a is the
diameter of the inner lead on the probe, /t R is the permeability of air, and $ is the permit-
tivity of Teflon.

10 ; However, measured reflection coefficient from analyzer 250 is not necessarily an accurate
representation of I\ due to errors caused by the container 206, the coaxial line 12, and
connectors at port A, for example. The Bao procedure reduces these errors, using a cali-
bration procedure based on a linear assumption. This assumption and the values collected
from the calibration procedure give rise to a matrix derivation

g= \ „ (3)
15 in which A, is a frequency dependent complex constant related to a scattering matrix.

During the course of experimentation, applicants realized that if analyzer 250 were
calibrated with port connectors and coaxial cables 12 attached, the analyzer output would be
r, whereupon use of the Bao matrix procedure would be unnecessary.

Thus, while equation (I) is valid, its real and imaginary components should be separated to
be effectively used by computer 280 during execution of a data processing routine, e.g., an
Excel spreadsheet program.

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Considcr then equations (4) and (5), in which p is the complex reflection coefficient output
from analyzer 250:

Heal ~1 i

Euler's formula is used as shown in equations (6) and (7) to convert equations (4) and (5)
to the more commonly encountered impedance magnitude and phase quantities:

Z e =tan- X 4^ (7)

Z Real

5 Referring back to Figure 5A, the various analytes in a blood specimen, especially small ion
electrolytes (also called blood electrolytes), can measurably affect the impedance and phase
angle. In an application in which glucose concentration is to be determined, what actually
may be measured with system 200 is the effect of glucose, e.g., X in Figure 5A, upon ions
or water dipoles in the specimen solution 204. Applicants have discovered at certain cross-
1 0 over frequencies output by system 250, the effects of other substances Y in the specimen
204, including electrolytes, can be reduced or nulled-out. For example, at a cross-over
frequency of about 2.5 GHz, the concentration effects of NaCl and most probably other
blood electrolytes in a blood specimen are nulled-out, without degrading glucose
concentration measurements. In an analytical scheme in which N equations would have to
15 be solved for N unknowns, the ability to null-out electrolyte concentrations effectively

reduces the number of variables and thus the number of equations that must be solved. The
end result is that glucose concentration can be determined with higher specificity and confi-
dence. Further, as described later herein, phase shift measurements (e.g., comparison
between transmitted and reflected signals) over a wide frequency regime provide a surpris-
20 ingly linear response to electrolyte concentration. The phase shift data can then be used to
compensate for NaCl concentration contributions to total impedance measurements made at
frequencies lower than the 2.5 GHz cross-over frequency.

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PCT/TO97/00719

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Whcn generator 260 outputs frequencies greater than perhaps 1 GHz or so, the specimen
impedance magnitude appears to be primarily a function of the ability of water dipoles to
respond in the presence of the resultant oscillating field in the vicinity of the probe(s). At
output frequencies less than perhaps 500 MHz, impedance magnitude seems to be more a
5 function of ionic response to the oscillating field in the vicinity of the probe(s). Within a
blood specimen, NaCl is an important source of such ions. At inberween frequencies, the
impedance function transitions.

Below approximately 500 MHz, glucose in the specimen solution appears to impede ionic
mobility in responding to the oscillating field, and thus the effective impedance increases.
10 For example, between about 10 MHz and 100 MHz, impedance change due to NaCl

concentration changes in the specimen are substantially stronger than impedance changes
due to concentration changes in glucose.

Applicants have discovered that at test frequencies below about 1 GHz, increasing
concentrations of NaCl decrease impedance magnitude ("Z"), and that at a cross-over fre-

15 quency of about 2.5 GHz, impedance measurements are sensitive to glucose concentration
but insensitive to electrolyte concentration. Further, applicants have learned that over a
wide frequency regime, phase shift increases linearly with increasing NaCl concentration,
with little or no effect due to changing glucose and/or albumin concentration. Thus, it
appears that at higher frequencies (e.g., above 1.5 GHz or so), larger molecules simply do

20 not respond sufficiently rapidly to meaningfully influence phase shift measurements. By
contrast, electrolytes, including NaCl, have small ions that can respond measurably with
respect to phase shift measurements. As described herein, collectively, these discoveries
provide measurement protocols to reliably and with specificity determine glucose concen-
tration, despite the presence of electrolytes of varying concentrations.

25 In Figure 5B, a non-invasive system for in-vivo testing is depicted. In this embodiment,
network analyzer or system 250, and computer system 280 may be identical to what was
described with respect to Figure 5 A. However, an electrode assembly 310 comprising two
metallic probes 320 spaced-apart perhaps 2.5 cm on a substrate 300 is used. Substrate 300
may be a sheet of single-sided copper clad printed circuit board measuring perhaps 5 cm x

3 0 7.5 cm. Electrodes 320 preferably are made from brass and are about 0.6 cm tall, 0.6 cm
wide, and about 1.2 cm in length. Spaced-apart faces of the probes define a surface slanted
at about 45°. Each conductive electrode 320 is connected to one coaxial cable 12. The
finger 4 of a subject to be tested for glucose concentration, for example, is pressed against
the slanted surfaces of the probes, thus completing an electrical circuit with coaxial cables

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12, and thus ports A and B ofanalyzer system 250. It is understood in Figure 5B, that
port A will receive back a portion of the transmitted signal as a reflected signal. Port B
will receive that portion of the transmitted signal that propagates through the specimen
tissue.

5 In practice, probe assembly 310 provides enhanced signal to noise ratio, and improved
repeatability relative to other probe designs, including the probe assembly depicted in
Figure I. Reliable data have been obtained with probe assembly 310, typically in the
frequency range of about 1 MHz to about 3 GHz. It will be appreciated that the config-
uration of Figure 5B is especially useful to laypersons, including suspected and actual
10 diabetics, who wish to monitor their own blood chemistry, especially glucose concentration
levels.

Figures 6A and 6B plot predicted and actual glucose concentration against time, for non-
invasively obtained test data (shown by "plus signs") and for invasively obtained data
(shown by "boxes"). Both figures depict the same experiment in which a human subject
15 drank water at 14:00 hours (2:00 P.M.) and ate food at 15:15 hours (3:15 P.M.) The non-
invasive test data were obtained using finger probes 320 such as shown in Figure 5B,
whereas invasive test data were obtained from actual blood samples from the subject.

Approximately 101 separate frequencies were used to obtain raw data during the experi-
ment. Figure 6A depicts non-invasive predicted glucose concentration based upon imped-
20 ance and phase data taken at about 17 MHz. The impedance and phase data were then
converted into predicted glucose concentration data using an algorithm.

In Figure 6A, predicted glucose concentration shows an increase at about 14:20 hours,
apparently corresponding to the subject's intake of water. In essence, the water has diluted
electrolyte concentration in the subject, which has caused predicted glucose concentration to

2 5 offset vertically, erroneously, by some 50 units. After 15:15 hours, the predicted glucose

level rises, which represents the subject's intake of food. Note, however, that the same 50
unit vertical offset is still present.

Using mathematical regression analysis to examine data for the approximately 101
frequencies used, applicants realized that non-invasive phase shift data taken at 103 MHz

3 0 would provide a correction for the 50 unit error offset in non-invasive glucose predictions

taken at 17 MHz.

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Figure 6B shows the same experiment, now plotted with correction data taken at 103 MHz,
in which "plus signs" depict predicted non-invasive glucose concentration data from the
subject using 17 MHz transmission-mode impedance magnitude data as corrected by the 103
MHz phase shift data. Clearly the use of the higher frequency .phase shift correction has
5 largely compensated for the 50 unit offset (present in Figure 6A but not in Figure 6B) f re-
sulting from water dilution of electrolytes.

In general, Figure 6B shows close agreement between actual invasively measured glucose
concentration, and non-invasively predicted glucose concentration. Although not fully
appreciated by applicants at the time the subject experiment was conducted, it appears that

10 the 103 MHz phase shift data provides a good measure of electrolyte concentration

including the effects of electrolyte dilution. At 103 MHz, small ion electrolytes including
NaCl could respond to the oscillating field, whereas larger glucose molecules could not,
and thus would not substantially influence the measurement. By contrast, the 17 MHz data
provided a measure of glucose and electrolyte concentration, which data when compensated

15 for by the 103 MHz electrolyte concentration data provided a truer measure of predicted
glucose concentration.

Collectively, Figures 6A and 6B suggest the wisdom of using data obtained at different
frequencies or frequency regimes (e.g., 17 MHz and 103 MHz in this example), to measure
different parameters (e.g., total impedance, and phase shift), to provide a measure of
20 compensation to more accurately arrive at the desired data (e.g., glucose concentration)
with a greater specificity confidence level.

Figure 7A depicts the startlingly linear relationship observed by applicants between NaCl
concentration and phase shift between transmitted and reflected signal at a specimen. In
Figure 7A, various frequencies between 2.25 GHz and 2.75 GHz were used, phase

25 difference was between two probes, e.g., probes 202 A/B in Figure 5 A. The experiment
began with distilled water, which at shown at the bottom of the graph had 0 radian phase
shift. Adding increments of 20 mM NaCl to the distilled water showed a very linear rela-
tionship: higher NaCl concentration increased the measured phase shift rather linearly. At
the very top of the graph, data were obtained first for 300 nM NaCl, after which two 100

3 0 mg/dL of glucose powder was added to the salt water solution. As seen, in the 2.25 GHz
to 2.75 GHz frequency regime displayed, changing glucose concentration (indeed a rather
substantial change in glucose concentration) did not affect phase shift measurements,
whereas changing NaCl concentration produced a linear change in measurable phase shift.

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Figure 7B is averaged phase shift data obtained with two probes, using frequencies ranging
from 2.0 GHz to 2.5 GHz, in which varying concentrations of NaCl, glucose, and albumin
were added to a baseline solution of phosphate buffered saline ("PBS"). PBS was used in
that it mimics the electrolyte environment of blood well, without proteins or other
5 substances being present in the solution.

Consistent with the findings of Figures 6A and 6B, increasing NaCl concentration increased
phase shift in a linear fashion in Figure 7B. Of special significance, however, is the bot-
tommost portion of the graph, which corresponds to a phase shift of about 0.11 radians for
a 246 mg NaCl solution. This data line remained constant, even when 40 mg (100 mg/dl)
10 and then 80 mg (200 mg/dl) glucose were added, and even when 100 mg (250 mg/dl)

albumin was further added. The data of Figure 7B demonstrates that the linear phase shift
measurable for varying electrolyte concentration is not meaningfully influenced by glucose
concentration and/or albumin concentration.

Figure 7C is a composite graph that demonstrates that a cross-over frequency of about 1.5
15 GHz renders phase shift measurements highly insensitive to varying albumin concentrations
in a PBS solution. In Figure 7C, the bottommost trace at about 0.017 radians represents
phase shift caused by changing concentration of gamma globulin by 5 g/dl, and the trace at
0,005 radians represents phase shift caused by changing concentration of gamma globulin
by 2.5 g/dl. The uppermost trace in Figure 7C represents phase shift due to intralipids at
20 1.4 g/dl concentration, the trace at -0.02 radians represents a different analyte with glucose,
not herein relevant, and the -0.015 phase shift represents intralipids at 0.7 g/dl concentra-
tion. Of special interest are the three tracelines centered about 0 radian phase shift. The
trace at -0.005 radians represents albumin at 5 g/dl concentration, the trace at about -
0.0025 radians represents albumin concentration of about 2.5 g/dl, and the trace at 0 phase
25 shift is the baseline PBS. The various concentrations above noted are substantially greater
in magnitude than variations that would ever occur in a human being. Note that at a fre-
quency of about 1.5 GHz, phase shift is substantially insensitive to albumin concentration
level. Thus, by measuring different characteristics associated with a specimen at different
frequencies or over different frequency regimes, the effects of various constituents can be
3 0 nulled-out. In the example of Figure 7C, greater measurement specificity is attained for a
desired analyte, e.g., glucose, in the presence of other substances, e.g., albumin.

Figure 7D depicts phase shift data between about 300 KHz and 100 MHz for changing
concentrations of glucose, the glucose being added to sheep blood in increments of 250

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mg%. It is seen that at about 20.1 MHz, phase shift data is insensitive to glucose
concentration.

Figure 8A depicts magnitude impedance data measured in a sheep blood baseline solution,
for various glucose concentrations, using frequencies ranging from 0.3 MHz to 1.0 GHz.
5 Over this extremely wide frequency regime, increasing concentrations of glucose increase
impedance. The relative change of glucose concentration upon impedance is greater at
frequencies lower than about 0.5 GHz, no doubt because at lower frequencies the large
glucose molecules exert greater hinderance upon ion movement.

In general, applicants have learned to appreciate that impedance measurement accuracy is
10 higher at low frequencies than at higher frequencies. Thus, as will be seen, impedance

measurements at 2.5 GHz can provide a measure of glucose concentration nulling-out NaCl
and other electrolyte concentrations, the equipment measurement sensitivity is substantial
less than at say 100 MHz. For example, a measurement sensitivity of 0.1 Q is a good
design goal. However, at 2.5 GHz, impedance magnitude sensitivity will be about l/25th
15 the sensitivity at 100 MHz. Thus, as described herein, a recommended protocol will

involve impedance and/or phase measurements in the GHz range, as well as measurements
at much lower frequencies.

Figures 8B depicts impedance change when a specimen of sheep's blood has glucose added,
but relatively little change when concentrations of NaCl are added. The bottommost plot

20 (with •boxes") is baseline sheep blood with a declotting agent. One addition of NaCl was
then added (equivalent to change in concentration of 10 mM), and data taken at five minute
intervals for the next five runs. During the last (uppermost) four runs, glucose was added.
Glucose additions clearly increase the measured impedance. Note that, contrary to behavior
at lower frequencies, adding NaCl in the 2.94 to 3 GHz regime actually increased im-

25 pedance, probably due to an interaction of ions with water molecules.

In Figure 8C, impedance data were obtaining using frequencies ranging from about 2.42
GHz to about 2.48 GHz, Again, a baseline solution of sheep blood (drawn with "boxes")
was used, into which one addition of NaCl was made, followed by four additions of
glucose. For the NaCl additions, essentially no impedance change results in this frequency
30 regime. However, the uppermost four runs, which represent addition of increasing

concentrations of glucose, clearly increase impedance in this frequency regime. Thus,
impedance measurements in a frequency regime of about 2.42 GHz to about 2.48 GHz are
sensitive to glucose concentration, and are insensitive to NaCl and other small ion elec-

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trolyie concentrations. While sheep blood was used as the specimen, similar results are
obtainable with human blood. Further, as noted earlier, the human body maintains tight
homeostatic control over concentrations of most electrolytes, proteins and lipids within the
blood.

5 Figure 8D depicts impedance data for a frequency regime of about 2 GHz to about 2.1 GHz
for a baseline of sheep blood (drawn with "boxes"). In the bottommost runs, the addition
of NaCl (10 mM concentrations increments) caused a decrease in impedance. However, in
the uppermost four runs, additions of glucose clearly increased impedance in a linear
fashion.

10 Figure 8E depicts impedance magnitude measurements made using frequencies ranging

from about 2.25 GHz to 2.75 GHz, with a specimen of distilled water into which increasing
concentrations of NaCi were added. The bottommost traces represent distilled water
baseline data, and the remaining traces reflect increasing concentrations of NaCl, with the
uppermost trace representing highest concentration (200 mM NaCl). Interestingly, the

15 effect of increasing NaCl concentration upon impedance varies non-Iinearly with frequency.
The right portion of Figure 8E demonstrates that impedance increases with increasing NaCl
concentration (a result opposite to what is encountered below about 1 GHz). By contrast,
the left portion of Figure 8E shows first an increase and then a decrease in impedance as
NaCl concentration increases (e.g., as more Na or CI ions are added to the test solution).

2 0 Figure 8F demonstrates that use of a frequency of about 2.5 GHz can null-out essentially all
changes in NaCl concentration upon impedance measurements. The data shown in Figure
8F were gathered using a distilled water specimen into which increasing concentrations of
NaCl were added. At the approximately 2.5 GHz cross-over frequency, all curves inter-
sected, independently of NaCl concentration. Note that the NaCl concentrations used in

25 Figure 8F included the human physiological range of about 135 mM to 145 mM NaCl.

Figure 8G depicts average impedance as a function of frequency ranging from about 1 MHz
to about 0.4 GHz. Note that between about 0. 1 and 0.2 GHz, gamma globulin appears to
saturate.

In other experiments, applicants measured impedance magnitude using PBS at various
3 0 temperatures to determine temperature sensitivity. These experiments disclosed that use of
frequencies ranging from about 800 MHz to about 900 MHz provided impedance magnitude
data that was temperature insensitive. The measurements were made using reflective mode,

WO 97/39341 PCT/IB97/00719

-27-

bm the same result would apply to transmitted mode data. When using a non-invasive in-
vivo measurement configuration such as shown in Figure 5B, skin temperature at a
subject's fingers can range from about 24°C to about 37°C. In practice, it is recommended
that in addition to other data, that data also be taken in the 800 MHz to 900 MHz
5 temperature insensitive regime, to provide a measure of correction as needed for the other
data.

To recapitulate, the present invention recognizes that electrolyte ion interference, especially
NaCl, with glucose measurements can be reduced. In one application, the interference is
effectively nulled out, using impedance magnitude measurements at a cross-over frequency.
10 In another application, compensation for electrolyte ion effects upon glucose measurements
are made. The configuration of Figure 5A and likely that of Figure 5B can predict total
glucose concentration with acceptable specificity and error tolerance.

As noted, it is advantageous to make high frequency and low frequency measurements of
various parameters to provide a good glucose concentration prediction (with good specifici-
15 ty) in a specimen. Preferably, low frequency regime data is taken over 21 or more

frequencies, and high frequency regime data is taken over 81 or more frequencies. While
the preferred embodiment used a network analyzer that provided discrete frequencies, one-
at-a-time, the various frequencies could instead have been presented en masse, or as groups
of frequencies, rather than as discrete separate frequencies.

20 High frequency, e.g., 1 GHz to perhaps 5 GHz, measurements of phase provide a good
measure of electrolyte concentration, in which frequency regime the phase measurements
are insensitive to glucose concentration. On the other hand, use of a 2.5 GHz cross-over
frequency permits impedance magnitude indication of glucose concentrations, with little
contribution from electrolyte concentrations. But the most sensitive measures of glucose

25 concentration are obtained at lower frequencies, at which impedance magnitude is a
measure of glucose concentration plus electrolyte concentration.

High frequency phase response was used to predict changes in NaCl concentration. This
predicted NaCl concentration change was then used to predict the impedance magnitude
change at low frequency due to electrolyte concentration change. The predicted low
30 frequency electrolyte contribution was then subtracted from low frequency total impedance
magnitude. The remainder was impedance change due to glucose concentration. In mathe-
matical terms:

WO 97/39341 PCT/IB97/00719

-28-

A[NaCl] = CALjrURVENaClPHASEHl * APhase @ high frequency AZ*^ =
CAL^CURVE_NaCl_MAG__LO * A[NaCl)

A[Glucose] = CAL_CURVE_GLU_MAG_LO * AZ^

5 The "CALCURVE* expression is derived from calibration equations. When calculating
concentration changes from phase or impedance change, it is necessary to solve an
appropriate calibration equation for an unknown, e.g., "x" in terms of a know, e.g., "y\
NaCl calibration was made using a PBS baseline solution into which NaCl was added in 2
mM increments, up to 12 mM above normal PBS. A second NaCl calibration involved di-

10 luting a PBS solution with distilled water in 2 mM increments, to -12 mM from normal
PBS, during which time the solution volume changed from about 588 pi to about 685 jd.
However, the resultant calibration curve provided a linear response with an excellent fit,
e.g., R 2 >0.999. Glucose calibration involved three separate experiments using -10 mM
PBS, normal PBS, and + 10 mM PBS baseline solutions, into which glucose was added in

15 100 mg/dL increments to 500 mg/dL. The glucose response was quite linear with good
correlation for the calibration curve.

In making experimental runs, error was defined as 100* (Predicted value - Actual value) /
Actual value. On a run-to-run basis, NaCl concentration predictions were <3% and
overall NaCl concentration predictions have <0.2% error. Overall, glucose concentration
20 predictions had <13% error, and run-to-run glucose predictions had <23% error. These
results are gratifying, although future embodiments will no doubt return even more accurate
glucose predictions.

The prediction method has the advantage of being fairly sensitive to NaCl, whose low
frequency response is stronger than that of glucose. Although NaCl changes may be

25 predicted with accuracy using high frequency phase data, any error in such measurement
tends to be "magnified" by the leveraging effect of NaCl at low frequencies relative to
glucose. Ideally, compensation would occur at some frequency whereat the NaCl response
and glucose response were closer in magnitude. Applicants are also examining use of
mathematical derivatives of the impedance and phase data obtained with the present inven-

3 0 tion.

Modifications and variations may be made to the disclosed embodiments without departing
from the subject and spirit of the invention as defined by the following claims.

WO 97/39341 PCT/IB97/00719

-29-

WHAT IS CLAIMED IS:

1. A method for determining concentration of a first chemical in the presence
of a second substance in a specimen, the method including the following steps:

(a) subjecting said specimen to radio frequency signals having a frequency
5 regime ranging from about 0.1 MHz to about 5 GHz;

(b) at a first frequency regime, using at least some of said radio frequency
signals to obtain data proportional to magnitude of concentration of said second substance in
said specimen;

(c) at a second frequency regime, using at least some of said radio frequency
10 signals to obtain data proportional to combined concentration in said specimen of said first

chemical and said second substance; and

(d) using data from said first frequency regime and data from said second
frequency regime to obtain a measure of concentration of said first chemical in said
specimen.

15 2 - The method of claim 1, wherein said specimen includes blood.

3. The method of claim 1, wherein said specimen includes blood t said first
chemical includes glucose, and said second substance includes NaCl.

4. The method of claim 1, wherein at step (a), at least some of said frequen-
cies are presented sequentially.

20 5. The method of claim 1, wherein at step (a), at least some of said frequen-

cies are presented simultaneously.

6. The method of claim 1, wherein at step (b), said first frequency regime
ranges from about 1 GHz to about 3 GHz.

7. The method of claim 1, wherein at step (b), said data proportional to

2 5 magnitude is obtained by measuring phase shift between radio frequency signals input to
said specimen and radio frequency signals returned from said specimen.

8. The method of claim 1, wherein at step (c), said second frequency regime
ranges from about 0. 1 1 MHz to about 3 GHz.

WO 97/39341 PCT/IB97/00719

-30-

9. The method of claim 1, wherein at step (c), said second frequency regime
ranges from about 800 MHz to about 900 MHz, in which regime temperature effects upon
data are minimized.

10. The method of claim 1, wherein at step (c), said data proportional to com-
5 bined concentration is obtained by measuring magnitude of impedance at said specimen.

11. The method of claim 1, wherein at step (d) a concentration value deter-
mined in step (b) is subtracted from a combined concentration determined in step (c) to
provide said measure of concentration of said first chemical.

12. The method of claim 1, in which said method is carried out non-invasively
10 on a human subject, and wherein step (a) includes coupling said radio frequency signals via

at least one probe that contacts a distal portion of said subject's body.

13. A method for determining concentration of a first chemical in the presence
of a second substance in a specimen, the method including the following steps:

(a) subjecting said specimen to radio frequency signals at a cross-over

15 frequency at which frequency concentration effects of said second substance are essentially
nulled -out; and

(b) determining from data taken at said cross-over frequency concentration of
said first chemical.

14. The method of claim 13, wherein said specimen includes blood, said first
20 chemical includes glucose, and said second substance includes NaCl.

15. The method of claim 14, wherein said cross-over frequency is about 2.5

GHz.

16. The method of claim 13, wherein at step (b), said data is impedance data.

17. The method of claim 13, wherein step (a) is carried out non-invasively on
25 a human subject by coupling said cross-over frequency via at least one probe that contacts a

distal portion of said subject's body.

18. A system for determining concentration of a first chemical in the presence
of a second substance in a specimen, including:

WO 97/39341 PCT/D397/00719

-31-

a transmitter outputting radio frequency signals having a frequency regime ranging
from about 0.1 MHz to about 5 GHz;

at least one probe, coupling to said transmitter, contacting a portion of said
specimen; and

5 a receiver-signal processor system, coupled to said at least one probe, that analyzes

at least some of said radio frequency signals present at said probe;

said receiver-signal processor system providing data including at least impedance
and/or phase shift present at an interface between said specimen and said at least one probe;
wherein data provided by said receiver-signal processor system is used to deter-
10 mine said concentration of said first chemical in said specimen.

19. The system of claim 18, wherein said specimen is human blood, said first
chemical is glucose, said second chemical includes NaCl, and wherein transmitter includes
a network analyzer.

20. The system of claim 18, wherein:

15 said specimen is a human subject including said subject's blood;

said first chemical is glucose;
said second chemical includes NaCl; and

said at least one probe contacts an exterior portion of a finger of said subject such
that non-invasive data is provided by said system.

20 21. A non-invasive method for determining concentration of at least a first

constituent in the presence of a second constituent in a specimen, the method including the
following steps:

(a) subjecting said specimen to radio frequency signals having a frequency
regime ranging from about 0.1 MHz to about 5 GHz;
25 (b) at a first frequency regime, using at least some of said radio frequency

signals to obtain data proportional to magnitude of concentration of said second constituent
in said specimen;

(c) at a second frequency regime, using at least some of said radio frequency
signals to obtain data proportional to combined concentration in said specimen of said first

3 0 constituent and said second constituent; and

(d) using data from said first frequency regime and data from said second
frequency regime to obtain a measure of concentration of said first constituent in said speci-
men.

WO 97/39341 PCT/IB97/00719

-32-

22. The method of claim 21, wherein said sample includes in vivo blood,
wherein said first constituent is hematocrit in said in vivo blood, and wherein said second
constituent includes at least one chemical whose concentration in said in vivo blood can
affect a measured concentration of said first constituent in said specimen.

WO 97/39341 PCT/EB97/00719

1/14

SUBSTITUTE SHEET (RULE 26)

WO 97/39341

PCT/IB97/00719

O
CO

co ai

o
in

O-C

■—MA— ■

o
to

-If-

S QJ

IS
CO -J

o
o

o
in

SUBSTITUTE SHEET (RULE 26)

WO 97/39341

PCT/IB97/D0719

4/14

SUBSTITUTE SHEET (RULE 26)

WO 97/39341

5/14

PCT/IB97/00719

Relative Deviation

7 10 15 20

FREQUENCY - N*30 MHz

FIG. 4C

SUBSTITUTE SHEET (RULE 26)

WO 97/39341

PCMB97/00719

SUBSTITUTE SHEET (RULE 26)

WO 97/39341

PCT/IB97/00719

8/U

250

200

150

§ 100

-J

+
+

— t

J- +

+ +

^ m

1 i

•m 1

13:4514:00 14:15 14:30 14:45 15:00 15:15 15:30 15:45 16:00 16:15 16:30

TIME

FIGURE 6A

250

200

£ 150

i ■ t

100

+
+

13:4514:00 14:15 14:30 14:45 15:00 15:15 15:30 15:45 16:00 16:15 16:30

TIME

Hl FIGURE 6B

SUBSTITUTE SHEET (RULE 26)

WO 97/39341

PCI7TB97/00719

9/14

PHASE
SHIFT
0.35

Last series:

300nM NaCI, no additions, and
2 additions of 100 mg/dL of
glucose powder.

2.25GHz

FIGURE 7A

PHASE
SHIFT

0.02-
0.04-
0.06-

^0.08-f
a

o.H

0.12
2.00

BASELINE

/-23n)g NaCI=10niM change^

46mg NaCI

-146mg NaCI

_^80jMNaCI

_£240mM NaCI
72201

2.75GHz

-100mg Albumin-250mg/dL

rno change / ^40rag G lucose=100mg/dL

-246«g NaCI / ^Omg Glucose=200mg/dL

E*09 I 2.DE+09 I 2iOE+09 I 230E+09 I 2.40E4W I 2.50E+09
2JJ5E+09 2.15E+09 2.25E+09 2.35E+09 2.45E409

FREQ.

SUI

26)

WO 97/39341

PCT7IB97/00719

10/14

1-10E+9 I 1J0E+9 • 1.50E+9 I 170F+9 i 190F+Q

1.00E+9 120E+9 ,JUt+9 1.40E+9 1.60E+9 U0E+S 1M+9

Frequency
FIGURE 7C

2.00E+9

SHIFT

100000 nxoooo 20100000 30100000 4000000 soooooo andoooo 7000000 mm 9000000

20.1 MHZ

Frequency

FIGURE 7D

SUBSTITUTE SHEET (RULE 26)

WO 97/39341

PCT/IB97/00719

11/14

IMPEDANCE

mnn - , * SUT = SHEEP WH0LE BL00D

J T ose * ANALYTE = GLUC0SE

rSOoInar 9 a lucose ,ajUD0SE ^ W ^ DRY T0 40 BLOOD,
g. giu *FREQ. RANGE = 300kHZ TO 1 GHz

*TEMP = 30 DEG.C.

♦PROBE 1 IS TEST PORT (ADDITIONS TO THIS PORT)
♦PROBE 2 IS CONTROL PORT.
♦RUNS SEPARATED BY 14 MINUTES BETWEEN BEGINNING
OF ONE RUN TO BEG. OF NEXT RUN.
♦PROBE 1 ON PORT 1 AND PROBE 2 ON PORT 2.

■BASELINE
-250mg% glucose

1.00E+5 1.00E+8 2.00E+A 3.00E+8 4.00E+8 5.00E+8 6.00E+8 7.00E+8 8.00E+8 9.00E+8 1.00E+9

Frequency
FIGURE 8A

3.6

Glucose added

2.94E+9

2.95E+9 2.96E+9 2.97E+9 2.98E+9 2.99E+9 3.00E+9
Frequency

FIGURE 8B

SUBSTITUTE SHEET (RULE 26)

WO 97/39341

PCT/IB97/00719

12/14

6.5

glucose added

4.7

2.42E+9 2.43E+9

2.44E+9 2.45E+9 2.46E+9 2.47E+9 2.48E+9
Frequency

FIGURE 8C

6.5

^6.3-

I 6.1 +

S 5 .9 ■ ■

"S 5.7"
a.

5.5--

g.5.3

5 5.1
4.9 +

2D0E+9 2XE+9 2JJ2E+9 2iJ3E+9 2.04E+9 2.Q5E+9 2M+9 2.07E+9 2.08E+9 2.09E+9 2.1QE+9

Frequency

FIGURE 8D

SUBSTITUTE SHEET (RULE 26)

WO 97/39341

PCT/IB97/00719

13/14

0.5

—1.6 I 1 ■ 1 ■ i 1 1 ■ 1 i 1 ■ ■ ' i ■ ' ■ ' i < i i ■ I i i i i i i ■ i i i ■ i i i
2.25GHz Frequency 2.75GHz

FIGURE 8F

SUBSTITUTE SHEET (RULE 26)

WO 97/39341 PCT/IB97/00719

14/14

IMPEDANCE

Frequency

FIGURE 8G

SUBSTITUTE SHEET (RULE 26)

INTERNATIONAL SEARCH REPORT

Internationa] application No.
PCI7IB97/00719

A. CLASSIFICATION OF SUBJECT MATTER

1PC(6) :G01N 27/02, 33/50

US CL : Please See Extra Sheet.
According to International Patent Classification (IPC) or to both national classification snd IPC

B. FIELDS SEARCHED

Minimum documentation searched (classification system followed by classification symbols)
U.S. : 73/53.01; 128/633, 635, 664, 665, 666; 324/642, 643, 644, 645, 646; 422/82.01; 436/63, 79, 95, 108, 149, 150, 151

Documentation searched other than minimum documentation to the extent that such documents are included in the fields searched

Electronic data base consulted during the international search (name of data base and, where practicable, search terms used)
Please See Extra Sheet.

DOCUMENTS CONSIDERED TO BE RELEVANT

Category*

Citation of document, with indication, where appropriate, of the relevant passages

Relevant to claim No.

Y,P

A
A

US 5,508 r 203 A (FULLER et al.) 16 April 1996, see entire
document.

P. M. J. M. de Vries et al. "Implications of the Dielectric
Behavior of Human Blood for Continuous Online
Measurement of Haematocrit" Medical & Biologiac!
Enginering & Computing, September 1993, Vol. 31, pages
445 - 448, see entire document.

US 4,679,426 A {FULLER et al) 14 July 1987.

US 4,765,179 A (FULLER et al) 23 August 1988.

1-22
1-22

fx] Further documents are listed in the continuation of Box C. See patent family annex.

ID be of

ofctodd

sdefvac «to ftBcnl kms ci tit whkb k oet o

•cr

HUng 4**

<m priority cfcuco(t) or which m
ifeofi

•X*

ayufcftfcoi prior to the mtoaliocol fifing <Ute bm kter <b—

I otrviow lo • penoo ikUfad Btfasut

family

Date of the actual completion of the intematioriaJ tearch
02 SEPTEMBER 1997

Date of mailing of the international search report

14 SEP 1997

Name and mailing addresi of the IS A/US
Cooamwooer of Puna* and Trademarks

Wwhingio*. D.C. 20331
Facsimile No. (703) 305-3230

Authorized officer /

arlen:

Telephone No. (703) 30&-06S i

Form PCT/1S A/210 (second sheetXJuly 1992)*

INTERNATIONAL SEARCH REPORT

International application No.
PCT/IB97/00719

C (Continuation). DOCUMENTS CONSIDERED TO BE RELEVANT

Category*

C itatio n of document, with indication, where appropriate, of the relevant passage*

Relevant to claim No.

E. C. Burdette et al. "In Vivo Probe Measurement Technique for
Determining Dielectric Properties at VHF Through Microwave
frequencies" rera Transactions on Microwave Theory and
Techniques, April 198p, Vol, MTT-28, No. 4, pages 414 - 427.

M. A. Stuchly et al. "Dielectric Properties of Animal Tissues In
Vivo at Frequencies 10 MHz - 1 GHz" Bioelectromagnetics, 1981,
Vol. 2, pages 93 - 103-

R. Pottel et al. "Surface Transmission Probe for Noninvasive
Measurements of Dielectric Properties of Organ Tissues at
Frequencies between V MHz and 300 MHz" Biomedizuiische
Technik. 1990, Vol. 35, No. 7-8, pages 158 - 161.

-22

1-22

Form PCT/lSA/210 (continuation of »econd sheetXJuly 1992)*

INTERNATIONAL SEARCH REPORT

International application No.
PCT/IB97/00719

A. CLASSIFICATION OF SUBJECT MATTER:
USCL :

73/53.01; 128/633. 635, 664 t 665, 666; 324/642, 643, 644. 645, 646; 422/82.01; 436/63, 79, 95, 108. 149, 150, 151

B. FIELDS SEARCHED

Electronic data bases consulted (Name of data base and where practicable terms used):

STN search in BIOSIS, CA, and MEDLINE files search terms: waveform?, wave form?, distort?, deform?, anal?,
det##, detect?, determin?, meaaur?, monitor?, test?, tens?, radio freq?, salt, nacl. sodium chloride, glucose, dextran,
augar, radio(3a)frcq?(5a)spect?, blood, finger*. tiuue#, radio(3a)freq?, mhz, ghr, high, analysis, prob?, anten?,
electrode*

Form PCT/ISA/210 (extra sheet)(July 1992)*

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